The present invention relates to an apparatus for replacing underground pipe.
Underground pipes are subject to inevitable deterioration and wear and, therefore, must be replaced from time to time. An obvious method for replacing existing underground pipe is to excavate the entire length of the existing pipe, remove it and place new replacement pipe into the excavation. Excavation of existing pipe is time-consuming, labor-intensive and results in damage to the area surrounding the excavation. In many instances pipes often lie beneath driveways, buildings, or gardens, and property owners are very concerned about any damage that may result thereto. In addition, excavation is often made difficult by the presence of underground utilities.
Accordingly, it is an object of the present invention to provide an apparatus and method for replacing underground pipe requiring minimal excavation.
Other devices and methods have previously been proposed for use in replacement of underground pipes and mains. For example, those disclosed in U.S. Pat. No. 6,171,026 issued to Crane et al.; U.S. Pat. No. 6,092,553 issued to Hodgson; U.S. Pat. No. 5,544,977 issued to Crane et al.; U.S. Pat. No. 4,720,211 issued to Streatfield et al.; and U.S. Pat. No. 4,738,565 issued to Streatfield et al. However, all of the devices and methods disclosed by the above patents suffer from several drawbacks.
Often the earth surrounding underground pipes is extremely hard because it has been compacted or has settled over the years that the pipes have been in the ground. Many of the tools of the prior art, such as those described in U.S. Pat. No. 4,720,211 issued to Streatfield et al., and U.S. Pat. No. 5,098,225 issued to Rockower et al., involve the movement outwards of fragments of the existing underground pipe and expansion of the cavity thereof in order to create a cavity large enough to accommodate a replacement pipe. Obviously, in very compact earth, expansion of the cavity of the existing underground pipe can be very difficult and sometimes impossible. In addition, expansion of the existing underground pipe can damage nearby underground utilities or surface features (e.g. where an existing pipe passes under a sidewalk the sidewalk, may be cracked by expansion of the cavity of the existing pipe).
Therefore it is an object of the present invention to provide an apparatus and method for replacing underground pipe that permits the expansion of the cavity of the existing underground pipe in hard, compacted, or settled earth.
It is a further object of the present invention to provide an apparatus and method for replacing underground pipe that permits the expansion of the cavity of the existing underground pipe while minimizing the risk of damage to surrounding utilities.
It is a further object of the present invention to provide an apparatus and method for replacing underground pipe that permits the replacement of an existing underground pipe with a larger diameter replacement pipe.
The invention is a tool for replacing underground pipe. The tool has a nose with a nose coupler for coupling a pulling chain for pulling said tool through the underground pipe, a rear portion with a rear coupler for coupling a retaining chain, a plurality of breaking elements extending along the central longitudinal axis from the nose to the rear portion, a plurality of nozzles on the rearward facing edges of the breaking elements, the nozzles operative to emit jets of high-pressure water against the surrounding soil and fragments of the underground pipe.
Each of the breaking elements extends radially outwardly from the central longitudinal axis and defines a breaking edge, which is angled outwardly from said central longitudinal axis such that the distance between the breaking edge and the central longitudinal axis increases with the distance from the nose. The distance from the central longitudinal axis to the outermost point of the breaking elements is greater than the radius of the underground pipe. The breaking edges are operative to fracture the underground pipe as the tool is drawn therethrough. Each of the breaking elements additionally defines a rearward facing edge.
In one embodiment a high-pressure hose is coupled to a coupling point on the rear portion of the tool, and is operative to supply water to the nozzles. The high-pressure hose is drawn through the underground pipe behind said tool.